446 https://www.id-press.eu/mjms/index Scientifc Foundation SPIROSKI, Skopje, Republic of Macedonia Open Access Macedonian Journal of Medical Sciences. 2020 Aug 05; 8(B):446-450. https://doi.org/10.3889/oamjms.2020.3355 eISSN: 1857-9655 Category: B - Clinical Sciences Section: Neurology Blue Light Exposure Improving Cognitive Function by Increasing Serum Orexin Level in Shift Working Nurse at Sanglah Central Hospital Denpasar Anak Agung Ayu Putri Laksmidewi*, Yuliantry Indah Lestari, Ni Putu Ayu Putri Mahadewi, I. Made Oka Adnyana, Anak Agung Bagus Ngurah Nuartha Department of Neurology, Faculty of Medicine, Udayana University, Sanglah Hospital, Denpasar Abstract BACKGROUND: Nurses are one of the many jobs that use the shift work system. Nurses work lovingly, requiring high attention when working. Sleep disorders are often experienced by nurses who work shifting outside of normal working hours. Long sleep disorders can cause cognitive function disorders. AIM: This study aims to determine the efectiveness of exposure to blue light in improving cognitive function and serum orexin levels compared to exposure to white light. METHODS: An experimental study with a pre-test-post-test control group design. Subjects were divided into treatment groups (exposure to blue light) and the control group (exposure to white light) equally. Both groups assessed cognitive function scores using the MoCA-INA and examined serum orexin levels before and after light exposure. RESULTS: The mean increase in the cognitive function score of the treatment group (5.00; p < 0.001) was greater than the control group (0.417; p = 0.054) and the mean increase in serum orexin levels in the treatment group (1068, 244; p < 0.001) was greater than the control group (336,706; p = 0.052), the increase in the treatment group was found to be statistically signifcant. CONCLUSION: Exposure to blue light before carrying out night shift can increase cognitive function scores 5 times greater and increase serum orexin levels higher than exposure to white light on nurses. Edited by: Slavica Hristomanova-Mitkovska Citation: Laksmidewi AAAP, Lestari YI, Mahadewi NPAP, Adnyana IMO, Nuartha AABN. Blue Light Exposure Improving Cognitive Function by Increasing Serum Orexin Level in Shift Working Nurse at Sanglah Central Hospital Denpasar. Open Access Maced J Med Sci. 2020 Aug 05; 8(B):446-450. https://doi.org/10.3889/oamjms.2020.3355 Keywords: Blue light; Orexin; Cognitive function *Correspondence: Anak Agung Ayu Putri Laksmidewi, Department of Neurology, Faculty of Medicine, Udayana University, Sanglah Hospital, Denpasar E-mail: laksmidewi2009@gmail.com Received: 12-Jul-2019 Revised: 16-Jul-2020 Accepted: 21-Jul-2020 Copyright: © 2020 Anak Agung Ayu Putri Laksmidewi, Yuliantry Indah Lestari, Ni Putu Ayu Putri Mahadewi, I. Made Oka Adnyana, Anak Agung Bagus Ngurah Nuartha Funding: This research did not receive any fnancial support Competing Interests: The authors have declared that no competing interests exist Open Access: This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial 4.0 International License (CC BY-NC 4.0) Introduction Nurses in work must remain vigilant and always full of love but sometimes can experience sleep disorders, especially those working with a rotating system. Disorders of sleep patterns afect circadian rhythms. Humans need sleep which is an active physiological process is needed for restoration and recovery, but the overall level of brain activity is not reduced during sleep. The rhythm of the human body is regulated by a part of the ventral anterior hypothalamus, the suprachiasmatic nucleus (SCN) located in the third ventricle at the top of the optic chiasm. SCN consists of two pairs of nuclei, namely, dorsomedial shell and ventrolateral core. The eferent fbers from the SCN will trigger nerve and humoral signals that will harmonize the circadian rhythm. The pineal gland in the brain works for a feedback mechanism to regulate SCN, inhibit melatonin production and excite orexin through the retinohypothalamic (TRH) tract and SCN. Lateral hypothalamic area (LHA) has three main neurons, namely, orexin neurons, MCH neurons, and neurons that contain glutamic acid decarboxylase (GAD) 65. Orexin neurons play a role in awake conditions, whereas GAD 65 and MCH neurons only play a role during sleep and especially during the rapid eye movement sleep (REMS) [1], [2]. The intensity of bright and dark light accompanied by a number of planned naps is an important factor in circadian rhythms which is a rhythmic biological process that afects 24-h mental, physical, and behavioral conditions that also regulate body temperature, blood pressure, and secretion patterns of the body. Signals from retina will be forwarded to an SCN oscillation system in the hypothalamus through the TRH tract. Giving blue light that has short waves (466–477 nm) at night is known to reduce melatonin levels in the blood and is associated with an increase in attention function and concentration [3], [4], [5]. Orexin is known to be associated with attention function, alertness, and concentration in awake conditions. Every sleep cycle, someone passes non-rapid eye movement and REM stadiums. During certain stages of sleep, there is an increase in brain oxygen absorption beyond normal when awake. Paradoxal